Solder ball connections have been used for mounting ICs (integrated computer chips) using the C-4 (controlled collapse chip connection) technology since first described in U.S. Pat. Nos. 3,401,126 and 3,429,040 by Miller. Packaging Electronic Systems by Dally (McGraw-Hill 1990 p. 113) describes flip chip or C-4 connections. In Dally, "Chip bond pads are deployed in an area array over the surface of the chip . . . These bonding pads are 5 mil in diameter on 10 mil centers. Matching bonding pads are produced on a ceramic substrate so that the pads on the chip and the ceramic coincide. Spheres of solder 5 mil in diameter are placed on the ceramic substrate pads . . . and the chip is positioned and aligned relative to the substrate. The assembly is heated until the solder spheres begin to soften and a controlled collapse of the sphere takes place as the solder simultaneously wets both pads. A myriad of solder structures have been proposed for mounting IC chips as well as for interconnection to other levels of circuitry and electronic packaging."
"Ball grid arrays: the hot new package" by Terry Costlow and "Solder balls make connections" by Glenda Derman both in Electronic Engineering Times Mar. 15, 1993, describe using solder balls to connect ceramic or flexible chip carriers to circuit boards.
Fabrication of multi-layer ceramic chip carriers is described in U.S. Pat. Nos. 3,518,756; 3,988,405; and 4,202,007 as well as "A Fabrication Technique For Multi-Layer Ceramic Modules" by H. D. Kaiser et al., Solid State Technology, May 1972, pp. 35-40 and "The Third Dimension in Thick-Films Multilayer Technology" by W. L. Clough, Microelectronics, Vol. 13, No. 9 (1970), pp. 23-30.
Fabrication of organic circuit boards is described in U.S. Pat. Nos. 3,554,877; 3,791,858; and 3,554,877. Thin film Techniques are described in U.S. Pat. Nos. 3,791,858.
U.S. Pat. No. 4,604,644 to Beckham describes materials and structures for encapsulating C-4 connections. U.S. Pat. Nos. 4,701,482 to Itoh and (Ser. No. 493,126 Mar. 14, 1990) to Christie et al. disclose epoxies and guidance in selecting epoxies for electronic applications.
Use of epoxy encapsulants to enhance fatigue life of flip chip connection is described in: D. Suryanarayana, R. Hsiao, T. P. Gall, J. M. McCreary, "Enhancement of Flip-Chip Fatigue Life by Encapsulation" IEEE Transactions on Components and Hybrids, and Manufacturing, Vol. 14, No. 1, pp. 218-223(1991);
J. Clementi, J. McCreary, T. M. Niu, J. Palomaki, J. Varcoe and G. Hill, "Flip Chip Encapsulation on Ceramic Substrates" Proc. of 43rd Electronic Components & Technology Conference Organized by IEEE at Orlando, Fla., June 1993, p. 175; D. O. Powell, and A. K. Trivedi, "Flip-chip on FR-4 Integrated Circuit Packaging", Proc. of 43rd Electronic Components & Technology Conference, Organized by IEEE at Orlando, Fla., June 1993., p. 182; Y. Tsukada, Y. Mashimoto, T. Nishio, and N, Mil, "Reliability and Stress Analysis of Encapsulated Flip Chip Joint on Epoxy Based Printed Circuit Packaging" Proc. of the 1992 Joint ASME/JSME Conf. on Electronic Packaging" vol. 2, Materials, Process, Reliability, Quality Control and NDE, (1992), p. 827; D. Wang and K. I. Papathomas, "Encapsulant For Fatigue Life Enhancement of Controlled Collapse Chip Connection (C4)", Proc. of 43rd Electronic Components & Technology Conferences, Organized by IEEE at Orlando, Fla., June 1993, p. 780; and in U.S. Pat. Nos. 4,999,699; 5,089,440; and 5,194,930 all to Christie, et al.
Problems with moisture induced cracking of plastic surface mount components and solutions thereof are described in: R. Lin, E. Blackshear, and P. Serisky, "Moisture Induced Cracking in Plastic Encapsulated Surface Mount Components During Solder Reflow Process," IEEE IRPS, 1988, pp. 83-89; B. K. Bhattacharyya, W. A. Huffman, W. E. Jahsman, and B. Natarajan, "Moisture Absorption and Mechanical Performance of Surface Mountable Plastic Packages," IEEE, 1988; B. Miles and B. Freyman, "The Elimination of the Popcorn Phenomenon in Overmolded Plastic Pad Array Carriers (OMPAC)," Proceedings of the Technical Conference of the IEPS, Austin, Tex., September 1992; G. S. Springer, Environmental Effects on Composite Materials, 1981, pp. 15-33; and in IPC-SM-786, December 1990.
Flexible film chip carriers (known in the art as ATAB) are described in U.S. Pat. Nos. 4,681,654; (Ser. No 07/009,981); and 5,159,535. In ATAB a flexible circuit board chip carrier is mounted on a circuit board using solder ball connect.
U.S. Pat. No. 5,147,084 to Behun, describes using a HMP (high melting point) solder ball in association with a LMP (low melting point) solder. FIG. 1A of that patent is described as follows. "A part 10 is to be joined to a board 11. Part 10 has internal metallurgy 14 which terminates at the surface at a bonding pads 12. A . . . LMP solder 16 is applied to a bonding pad 12. A . . . HMP solder ball 18 is placed in contact with LMP solder 16 and the assembly is heated to reflow the LMP solder which then wets to the non-molten HMP solder ball . . . Board 11 is also illustrated with internal metallurgy 15, terminating on the surface bonding pad 17 . . . the assembled part 10 . . . is brought into contact with part 11 having pad 17 and LMP solder 13, and the two are heated to a temperature sufficient to reflow the LMP solder but not sufficient to reflow the LMP solder but not sufficient to melt the HMP solder ball. The LMP solder 13 which is attached to the bonding pad 17, on board 11, will wet the HMP ball and connection will be achieved."
All these above, sources are hereby incorporated by reference.